The door sash of the vehicle door is provided with a weatherstrip made of a rubber-like elastic body for providing sealing between the door and a vehicle body 4 when the door is closed and a decorative resin sash molding 3 on the outer side of the door sash. In the case of a vehicle shown in FIG. 1, sash moldings 3 are attached to the outer side of the door sashes of a front door 1 and a rear door 2. As for the front door 1 shown in FIG. 2, the weatherstrip 8 providing sealing against the vehicle body 4 is attached around the door on the inner side.
The weatherstrip 8 consists of extrusion-molded parts 8a and die-molded parts 8b connecting the extrusion-molded parts 8a at the corners a and b in FIG. 1. In FIG. 2, the triangles are used to indicate that on the filled side thereof is a die-molded part 8b and on the non-filled side thereof is an extrusion-molded part 8a. 
FIG. 3 is an enlarged view of the part a shown in FIG. 1. FIG. 4 is a cross-sectional view at the line A-A in FIG. 3. As described above, the sash molding 3 is attached to the door sash. However, the sash molding end is generally not retained because there is no door sash there. An end cap 4 is simply attached to the end of the sash molding 3 as shown in FIG. 4.
The die-molded part 8b provided at the end of a weatherstrip and located at the end of a sash molding 3 has a fin 5 forming an insertion groove 7 in which the flange 6 of the door sash is inserted. Then, the sash molding 3 is attached to the door sash from the outer side and the fin 5 is held by the end cap 4 at the sash molding end, whereby the die-molded part 8b is retained by the flange 6.
The Japanese Laid-Open Patent Application Publication No. 2005-212219 relates to a retention structure for the belt molding end in a cross-section at the line C-C in FIG. 1 wherein, as shown in FIG. 5, a belt molding 11 having a sealing lip 10 that makes elastic contact with the window pane and an end cap 12 are set on a die and coupled by injecting a polymer material to produce a molded product assembly 13, the end cap 12 of the molded product assembly 13 is fitted on an outer door panel 14, and an engaging piece 15 integral-formed with the end cap 12 is engaged with the outer door panel 14 for retention.
The Japanese Laid-Open Utility Model Application Publication No. H05-32154 relates to a structure for mounting a dash side trim below the front pillar of a vehicle wherein, as shown in FIG. 6, one side wall of a U-shaped cross-section base 24 of a weatherstrip 23 fitted on the flange 22 of a front pillar 21 and a rib 26 formed on the side edge of a dash side trim 25 are coupled by a clip 27 so that the side edge of the dash side trim 25 is attached to the front pillars 21.
In the prior art structure shown in FIGS. 3 and 4, the die-molded weatherstrip fin 5 is not rigid and therefore it is difficult to fit the fin 5 on the flange 6. Then, poorly retained on the flange 6, the fin 5 can easily come off when the sash molding 3 is pulled. Once it comes off, it is difficult to put the fin 5 back on. Furthermore, it is difficult for rubber or resin material injected in a die during the die-molding to reach the corners of a cavity forming a thin fin 5. Then, problems occur that the fin 5 may have dents due to insufficient spread of the material or welded gas marks or the fin 5 may easily break during the release from the die.
The retention structure shown in FIG. 5 is a belt molding end retention structure, which is not a sash molding end retention structure. In this structure, a clip 12 is fixed to the belt molding end by injection molding. When assembled to a door panel, there is a door panel corresponding to the clip 12 and the clip 12 is directly attached to the door panel.
The retention structure shown in FIG. 6 is a dash side trim retention structure in which the side edge of the dash side trim 25 is attached to the flange 22 of the front pillar 21 together with the weatherstrip 23 in the manner that the weatherstrip 23 is first attached to the flange 22 together with the clip 27, then the rib 26 of the dash side trim 25 is inserted in the clip 27. The dash side trim 25 cannot be attached before the weatherstrip 23 is attached.